1. Field of the Invention
The present invention relates to a bicycle internal gear shifting hub and more particularly to a bicycle hub with an internal gear shifting mechanism, with the bicycle hub being mounted to the rear end of a bicycle frame and provided with an internal generator for powering a shift actuator mechanism.
2. Background Information
The mounting of an internal gear shifting hub to the rear wheel of a bicycle in order to enable the rider to reduce the amount of energy expended during pedaling by selecting a mechanically advantageous gear ratio is known. A conventional internal gear shifting hub includes a hub shaft mounted to the rear end of the bicycle frame, a drive cylinder that is rotatably supported around the hub shaft and transmits the pedaling force via sprockets and a chain, and a hub shell that is rotatably supported around the hub shaft. A power transmitting mechanism that transmits rotational force from the drive cylinder to the hub shell via one of multiple force transmission paths is disposed between the drive cylinder where the hub shell, and each force transmission path ordinarily has a unique gear ratio. The power transmitting mechanism includes a planetary gear mechanism that has one or more sun gears that are rotatably supported around the hub shaft. The power transmitting mechanism also includes a ring gear that is rotatably supported around the hub shaft, a planet gear carrier that is rotatably supported around the hub shaft, and multiple planet gears that are rotatably supported on the planet gear carrier that engage the sun gear(s) and the ring gear. Any of the multiple force transmission paths and the corresponding gear ratio are engaged by selectively linking various components with each other in a non-rotatable fashion. For example, one gear ratio is selected by non-rotatably linking the sun gear(s) with the hub shaft. Another gear ratio is selected by non-rotatably linking the drive cylinder with the planet gear carrier. Still another gear ratio is selected by non-rotatably linking the drive cylinder with the ring gear.
In recent years, an internal gear shifting hub has been developed where the shifting operation for selecting a force transmission path is carried out using a motor, for instance, as disclosed in Japanese Patent Laid-Open No. H10-230877. Such a motor driven shifting device is referred to as an electric internal gear shifting hub that directly manipulates the position of an operation member causing it to rotate. The operation member includes a rotating cam used to switch the force transmission path via a gear positioning unit that includes a motor.
Japanese Patent No. 3501781 discloses a hub in which the gear positioning unit and the internal gear shifting hub are linked via a gear shift cable and the operation member is remotely positioned. Electric power is supplied to the gear positioning unit by a power source, such as a battery, and the motor is driven via this electric power.
With a conventional internal gear shifting hub where the operation to switch the internal gear shifting hub is carried out using a gear positioning unit, the power from a power source such as a battery is supplied to the gear positioning unit or the like. Where the gear positioning unit is operated using power from the battery, if the battery runs out of power, gear shifting can no longer be performed unless the battery is replaced. As a result, where gear shifting is carried out using a gear positioning unit, it is difficult to perform stable gear shifting of the internal gear shifting hub for a long period of time.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved gear shifting design that overcomes the problems in the prior art. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.